The goal of this Mentored Research Scientist Development Award (K01) is to provide a career development and research training program that will enable the candidate to conduct innovative multi-method research on aggression and borderline personality disorder (BPD) in young women. BPD is disproportionately diagnosed among women in clinical and forensic settings and is associated with aggressive behavior in young women. However, aggression remains an understudied aspect of BPD and women's mental health. Evidence suggests that emotional deregulation mediates the relationship between BPD and aggressive behavior, but the precise affective processes underlying the association between BPD and female aggression are unclear. This study is designed to test a comprehensive biopsychosocial model of female aggression that articulates the potentially mediating role of difficulties regulating shame and anger, especially in the context of perceived interpersonal rejection, in the association between BPD and women's aggression. These processes will be assessed among a diverse inner-city sample of 120 emerging adult women (ages 18 to 22) using a multi-method approach that includes laboratory paradigms, psychophysiological measures, a 21-day ecological momentary assessment (EMA) protocol, clinical interviews, questionnaires, and official records. The multi-method approach will allow for fine-grained assessment of the topography of women's aggression that includes both direct and indirect (e.g., relational) forms across a variety of contexts. To examine the processes related to the maintenance and exacerbation of young women's aggression over the course of the year, aggression and other symptoms will be assessed at 6- and 12-month follow-ups by clinical interviews, questionnaires, and official records. Participants will be drawn from a community-based longitudinal study of girls' emotional and behavioral health (Pittsburgh Girls Study) with maximal variability in aggressive behavior and BPD features. The proposed project has three specific aims: 1) Examine associations between BPD features and women's affective and aggressive responses to social rejection in the laboratory; 2) Characterize associations between BPD features, affective experiences, and aggressive urges and behaviors in women's natural environments using EMA methodology; and 3) Integrate EMA and laboratory-based indices of shame and anger to test the validity of these measures for predicting trajectories of aggressive behavior over time. The candidate will receive in-depth training in the multi-modal assessment of aggression, psychophysiological assessment, EMA techniques, advanced statistics, and gender differences in the development and manifestation of aggression. Upon completion, the candidate will be poised to conduct high-impact research integrating lab-based and naturalistic assessments to understand the behavioral and biological mechanisms underlying women's aggression and BPD. Results will inform future intervention efforts designed to decrease female aggression and violence.